The effect of Mn substitution on microstructure and electrical properties of epitaxial BiFeO3 (BFO) thin films grown by an all-solution approach was investigated Raman analysis reveals that the Mn atoms substitution at Fe sites can result in Jahn-Teller distortion and thus lead to the weakness of long-range ferroelectric order. In addition, the break-down characteristics of BFO thin films are improved with the increase of Mn atoms content, although the leakage current is gradually increased. Meanwhile, the grain size, the dielectric constant and loss are also increased with the increase of Mn content. The P-E hysteresis loops and PUND results demonstrate that the intrinsic ferroelectric polarization is effectively improved with Mn atoms substitution as the grain size increased and Mn atoms play a role of nucleation sites However, the ferroelectric properties are deteriorated with the excess substituted Mn content due to the higher leakage current.